Finding the Fourth Proportional to 105.98, 159.00 and 85.86

Step by Step Solution

1. Step 1: Write the proportion equation
   105.98 : 159.00 = 85.86 : x
2. Step 2: Convert to fraction form
   105.98/159.00 = 85.86/x
3. Step 3: Cross multiply
   105.98x = 159.00 × 85.86
4. Step 4: Simplify right side
   105.98x = 13,651.42
5. Step 5: Solve for x
   x = 13,651.42/105.98
6. Step 6: Final answer
   x = 128.82